Abstract Understanding drought tolerance mechanisms of cassava is a pre-requisite to improve the performance of the crop in water-scarce regions. Several hypotheses have been formulated to suggest how cassava can withstand a prolonged period of drought. We performed field trials under drought conditions with a selection of 37 cassava genotypes to identify phenotypic and molecular patterns associated with drought tolerance. Plant morphologies varied significantly between cassava genotypes under drought conditions in Kenya, which indicates a strong genetic basis for phenotypic differences. Drought stress reduced yield by 59%, the number of edible storage roots by 43% and leaf retention by 50% on average. Over three years and in two experimental field sites, the most drought tolerant genotype bulked 7.1 (±2.1) t/ha yield while the most drought susceptible genotype yielded 3.3 (±1.4) t/ha under drought conditions. The significant positive correlation of yield under irrigated and non-irrigated conditions suggests that selection of genotypes with high yield performance under well-watered or control conditions should be prioritized to identify genotypes with superior performance under drought stress. The positive correlation between yield and leaf retention provided further evidence that leaf longevity positively contributes to yield in water-deficit conditions. Yield differences could be attributed in part to variation in stomatal conductance (gs) because selected drought tolerant genotypes maintained higher gs and delayed stomatal closure as compared to drought susceptible genotypes. Further analysis revealed that genetic or molecular differences for gs between drought tolerant and susceptible genotypes could be detected at early stages of water deficit. These differences likely involve both abscisic acid (ABA)-dependent and ABA-independent molecular pathways.

中文翻译：

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木薯耐旱性的形态生理学和分子学评价 (Manihot esculenta Crantz)

摘要 了解木薯的耐旱机制是提高缺水地区作物性能的先决条件。已经制定了几个假设来表明木薯如何能够承受长时间的干旱。我们在干旱条件下进行了田间试验，选择了 37 种木薯基因型，以确定与耐旱性相关的表型和分子模式。在肯尼亚干旱条件下，木薯基因型之间的植物形态差异很大，这表明表型差异具有很强的遗传基础。干旱胁迫使产量平均减少 59%，可食用储藏根数减少 43%，叶片保留量平均减少 50%。三年多来，在两个试验场，最耐旱的基因型增加了 7.1 (±2. 1) t/ha 产量，而最易受干旱影响的基因型在干旱条件下产量为 3.3 (±1.4) t/ha。灌溉和非灌溉条件下产量的显着正相关表明应优先选择在充足浇水或对照条件下具有高产量性能的基因型，以确定在干旱胁迫下具有优异性能的基因型。产量和叶片保持率之间的正相关提供了进一步的证据，即叶片寿命对缺水条件下的产量有积极贡献。产量差异可能部分归因于气孔导度 (gs) 的变化，因为与干旱敏感基因型相比，选定的耐旱基因型保持较高的 gs 和延迟的气孔关闭。进一步的分析表明，在缺水的早期阶段，可以检测到耐旱和易感基因型之间 gs 的遗传或分子差异。这些差异可能涉及脱落酸 (ABA) 依赖性和 ABA 非依赖性分子途径。